Based on how the Yellowstone plume slants now, Smith and colleagues projected on a map where the plume might have originated at depth when the hotspot was erupting at the Oregon-Idaho-Nevada border area from 17 million to almost 12 million years ago. They saw overlap, between the zones within the Earth where eruptions originated near the Oregon-Idaho-Nevada border and where the famed Columbia River Basalt eruptions originated when they were most vigorous 17 million to 14 million years ago. Their conclusion: the Yellowstone hotspot plume might have fed those gigantic lava eruptions, which covered much of eastern Oregon and eastern Washington state. “I argue it is the common source,” Smith says. “It’s neat stuff and it fits together.”

And from the KSL report. An animation of the extent of the magma chamber